Going inwardly from the outside, the walls of the housing comprise a multi-ply slab, one or more layers of elastomer coating, a plate of amorphous bitumen, and acoustic screens constituted by substantially contiguous parallel tubes which are filled with a solid material which is in the divided state and highly compacted, e.g. sand, or particles of graphite, or grains of silica. In addition, the enclosures include one or more blocks behind the loudspeakers and made of cellular foam with channels passing therethrough parallel to the axes of the loudspeakers.